US2474710A - Thread-trimming and pull-off mechanism for sewing machines - Google Patents

Description

June 28, 1949. A. R. WOOD l THREAD-TRIMMING AND PULLOFF MECHANISM FOR SEWING MACHINES 3 Sheets-Sheet l A Filed Aug. 2l, 1945 June 28, 1949. A. R. woon THREAD-TRIMMING AND PULL-OFF MEQHANISM FOR SEWING MACHINES 5 Sheets-Sheet 2 Filed Aug. 2l, 1945 June 28, 1949 A. R. WOOD l 2,474,710

THREAD-TRIMMING AND PULL-OFF MECHANISM FORSEWING MACHINES Filed Aug. 2l, 1945 5 Sheets-Sheet 5 Patented June 28, 1949 THREAD-.TRIMMING ANH),v PULL-.OFF MECH- ANISM FOB SEWING MACHINES Alfred R. Wood, Bridgeport, Conn., assignor to 'like Singer Manufacturing Company, Elizabeth,iN.. J., corporation of New Jersey Application August 21, 1945, Serial No`` 611,725.

(Cl. Ilm-252) -laims. l

The present invention relates to improvements in thread-trimming and pull-off mechanism for sewingmachines and is vespecially designed for those machines used for `stitching buttonholes, but it is not restricted to this special type, asit is capable of general application in all group stitch sewingymachines.

In sewing machines of this general group, it is common practice to provide a bobbin-thrcad trimmer and pull-off mechanism for severing the bobbin-th-read close to the work at the end of the buttonhol-ing cycle, and pulling from the bobbin a length of thread suiiicient to ensure the proper formation ofthe first stitch of' the next buttonhole. For successful operation, it is essential that the thread-trimmer and pulloi mechanism operates unerringly to sever the thread and pull from theV bobbin the proper length of thread, so that the shortest possible end of bobbin-thread will be left on the under side of theV buttonhole at the beginning` and ending of the sewing operation.

It is the primary object of the present invention to provide an improved tllread-trimming` and pull-off mechanism to secure a unilormlyY h-i-gh degree of- `certainty of operation of the mechanism in sewing operations on all of the various classes of material met with in practice.

It is another object off the invention to provide an improved pulloi which will draw from the bobbin a length of thread insuring the proper concatenation oi the sewing threads in the nrst stitch of the buttonhole and without leaving an excessively long end of Abobbin-thread requiring subsequent handl trimming.

Another object of the invention is to provide almechanism for carrying outthe above noted functions, which mechanism is exceedingly compact, outs the `thread close to the work with a high degree of accuracy, and operates over` a long period of time without requiring repeated sharpening.

To the attainment of the ends in view, the invention comprises the devices, combinations and arrangements of parts hereinafter described and particularly pointed out in the appended claims.

The features of the invention and the advantages attained thereby will be readily understood by those skilled in the art from the following detailed. description of a preferred embodiment of the invention illustrated in the accompanying drawings, `in which:

Fig. 1 is a fragmentary right side elevationalV View of a buttonhole sewing machine embodying the invention.

Fig. 2 is a `bottom plan view of the sewing machine.

Fig. 3 is a fragmentarybottom plan view ofthe cross-slide, bobb-in-thread trimming and pul'lnoff member and actuating means therefor, showing the bobbin-thread trimming and pull-oil member advanced to a position such that the pull-off finger is just engaging thebobbin-thread extending from the thread-case (not shown) up through the usual needle-aperture in the throat-plate, to the last stitch of the finished buttonhole.

Fig. l is a View similar to Fig. 3, but showing the thread-trimming and pull-Off. member slightly further advanced sothat the pull-oli `element is at substantially the end of its thread pull-off stroke andthe thread-trimming element is about to shear the bobbin-thread.

Fig. 5 is a similar View at a still later stage, after the bobbin-thread halsbeen severed, leaving a short thread-end extending from the last stitch in the completed buttonhole down through the needle-aperture in the throat-plate.

Fig. 6 is an enlarged top plan View of the assembled thread-trimming and pull-oil member.

Fig. 7 is a disassembled perspective view of' the thread-trimmingl and pullloff elements, showing the manner in which the, thread-trimming ele-v ment and the thread pull-ofi nger are attached to their common carrier.

' Fig. 8 represents an enlarged transverse ver tical sectional View taken substantially along the line 8 8, Fig. 5.

Fig. 9 represents an enlarged longitudinal vertical sectional view taken` substantially along the line 9 9, Fig. 3, showing the lead of the bobbinthread across the path of movement of the thread pull-oir nger from the thread-guide` on the` thread-casaup through the needleaperlllt` in the throat-plate to the last stitch of the comT pleted buttonhole.

Fig. l0 represents an enlarged longitudinal vertical vsectional view taken substantially along the line lll-Hl, Fiefi., Showing the lead of the bobbin-thread when the pulleoff ringer is in position of maximum pull-ofi.

Fig. 1l represents an enlarged longitudinal vertical `sectional view taken substantially along the line lIg-l I, Fig. 5 showing the thread seva ered by the cooperation of the thread-trimming knife and the vertically depressed ledger blade."

Referring in detail to the drawings, the invention is disclosed as embodied in a sewing mae chine of the type adapted to sew straight as distinguished from eyelet-end buttonholes;` the, constructive features of the illustrated machine being generally similar to those forming the subau ject of my United States Patent, NO. 2,411,493, issued Non 19, 1946 The machine-fram@sff r11-f1edlA with a bed l supporting astandard 2 of an overhanging bracket-arm terminating in a head 3. Mounted in the head 3 is a vibratory gate 4 carrying an endwise reciprocatory and laterally vibratory needle-bar fitted at its lower end with an eye-pointed thread-carrying needle Ii. The needle-bar 5 derives its reciprocations from the usual actuating connections within the head 3, which connections are operated lfrom the mainor arm-shaft (not shown) of the machine. The arm-shaft is connected by a vertical shaft 1 and gearing 8 (Fig. 2) to a loop-taker shaft 9 adapted to carry at its outer end a rotary loop-taker I0 for cooperation with the needle 6 in the formation of lock-stitches. In the machine illustrated in the drawings, the loop-taker I0 is of the rotary hook type and its constructive features are the same as those disclosedk in Patent No. 2,426,543, granted August 26, 1947. The lower or bobbinthread is housed in a thread-case II (Fig. which is journaled in the rotary hook III and restrained against rotation by an upstanding C- shaped rotation-restraining projection I2 cooperating with stops fixed to the machine-bed, As shown in Fig. 10, the top limb I3 of the rotationrestraining projection I2 is disposed beneath the usual cross-slide I4 and is provided with a leafspring member I5 beneath which the bobbinthread passes in its travel Ifrom the bobbin to the Work.

The work W to be buttonholed is adapted to be held in a work-clamp comprising the usual lower work-plate I6 and an upper clamp-foot I1. The upper clamp-foot I1 is carried by a resilient mem-I ber I8 (Fig. 1) which is secured at its inner end on a yoke I9 pivoted at 2l) to a lug 2I upstanding from the usual longitudinal slide-plate 22. The upper clamp-foot I1 is yieldingly urged downwardly into contact with the lower work-plate I6 by a coil-spring 23. To provide for separating the upper clamp-foot I1 from the lower work-plate I 6 for the insertion and removal of work, the yoke I9 is formed with a rearwardly extending taillever 24 adapted to underlie a roller l25 freely journaled on a stud '26 secured to a manually actuated lever 21 fulcrumed at one end on a stud 28 threaded into a supporting bracket 29. At its other end, the lever 21 is tted with a horizontally disposed stud 3B, to the lfree end of which lis attached a suitable treadle-chain connection-element (no-t shown). Depression of a suitable foottreadle will cause the lever 21 to swing on the stud 28, against the action of a spring 3|, thus causing the roller to engage the tail-lever 24 and swing the yoke I9 about its fulcrum 28, thereby raising the member I8 and the upper clampfoot I1. Y

To effect shifting of the work relative to the endwise reciprocatory and laterally vibratory needle 6, the work-clamp is slowly moved in stepby-step fashion, first away from the standard 2' and then towards the standard to cause the first and second rows of side zigzag stitches to be laid side by side in the work. At the opposite ends of its travel, the Work-clamp is shifted laterally to space the first and second rows of side stitches. The work-clamp derives its step-by-step movements and its lateral shift from the usual feedcam 32 carried on a vertically disposed feed-shaft 33 journaled in the bed and the bracket-arm of the machine. The connections between the workclamp and the feed-cam are identical with those disclosed in my previously mentioned Patent 2,411,493. are intermittently rotated by means of a oneway-acting clutch, indicated generally as 34, Fig.

The feed-cam 32 and feed-shaft 33- 4 2, of the well-known Horton type, which clutch is driven during the operation of the machine by means of an actuating lever 35 (Fig. 3) connected by a link 33 to a rock-lever 31. The rock-lever 31 is carried by the lower end of a vertically disposed rock-shaft 38, to the upper end of which is connected a rock-lever 39 (Fig. l) connected by a pitman 4I) to an eccentric 4I fast on the vertical shaft 1. When the shaft 1 is rotated, the eccentric 4I imparts to the rock-shaft 38 oscillatory movements whichthrough the rock-lever 31, link 35 and actuating lever 35, operate the clutch 34. The clutch drives the feed-cam 32 and the feed-shaft 33 intermittently in one direction.

rIhe bobbin-thread pull-olf and trimmer now to be described comprises a thread pull-off finger 42 and a hardened thread-cutting knife 43, both detachably mounted in substantial coplanar relation on a common oscillatory disk-like carrier 44. The carrier 44 is freely journaled on a pivotstucl 45 depending from the cross-slide I4 at substantially the geometric center of a circular clearance recess 43 cut into the under face of the cross-slide I4, The carrier 44 is yieldingly maintained in contact with the recessed bottom face of the cross-slide I4 and upon the pivot-stud 45 by a leaf-spring support 41 secured by a screw 43 to the cross-slide I4. The thread pull-olf finger 42 adjacent its free end is formed with a thread-engaging notch 49 and at its other end is provided with a washer-like shank 54 adapted to enter a segmental positioning-recess 5I formed in the bottom face of the carrier 44. The recess 5I at one side opens into the periphery of the carrier 44, as at 52, Fig. 7, to receive the bodyportion of the pull-off finger 42 and provide clearance on opposite sides of the nger, whereby the same may be adjusted relative to the carrier 44 and about the axis of the pivot-stud 45 to effect a change in the timing of the engagement of the pull-off finger with the bobbin-thread. The nger 42 is secured in its selected position of adjustment by the clamp-screw 53 which is threaded into the carrier 44.

Disposed in another recess formed in the top face of the carrier 44, Fig. 6, is the shank 54 of the thread-cutting knife 43, the knife being secured to the carrier preferably by two screws 55. The knife 43 is formed with a sharpened edge 56 which merges into a laterally extending pilot-extension 51. Cooperating with the sharpened edge 56 of the oscillatory knife 43 in severing the bobbin-thread, is a thin, iiexible, transversely reciprocatory ledger-blade 58 normally disposed in a transverse clearance-channel 59 (Figs. 4 and 5) cut into the under surface of the cross-slide I4. The ledger-blade 58 is formed with a shank 68 disposed at right angles to the body of the ledger-blade, which shank is secured to a trimmer-actuating slide-bar 5I endwise slidable in a suitable guideway provided in the under surface of the cross-slide I4. The slide-bar 3l carries at one end a rack 62 which meshes with teeth 63 segmentally formed in a portion of the periphery of the carrier 44, whereby the carrier is oscillated about the stud 45 during the actuation of the slide-bar. The means for actuating the slide-bar 3! comprises a bell-crank lever 54 (Figs. r1 and 3) pivoted at 55 to the bed I of the machine. The bell-crank lever 54 is operated by a link 56 connected to a vertically disposed lever 61 pivoted at 58 to the machine-bed I. The lever 61 is adapted to be vibrated when the manually actuated work- 2,474,71'o'ff the carrier; secondly, the manner in which. thel second knife member or ledger-blade 53 is arranged to travel in the clearancechannel 59, whereby it is disposed between the throat-plate carrying cross-slide I4 and the carrier 44; and thirdly, the use of the rack and gear drive between the carrier i4 and the transverse slide-bar 6i. The principal advantage gained from the compact arrangement of my present invention is that the carrier 4d, together with the pull-off member t2 and the knife 43, can be disposed in close proximity to the bottom of the throatplate and when so disposed, the resultant bobbinthread-end extending from the Work is exceedingly short. The provision of the two opposing spring members 4l and 'i4 results in yieldingly maintaining the two thread-cutting members d3 and 58 in effective shearing relation during their entire thread-severing action. The resultant scissors action is such as to minimize the resharpening requirements of the two knives @i3 and 5B.

Having thus set forth the nature of the invention, what I claim herein is:

1. In a sewing machine having a work-support, in combination, stitch-forming mechanism including at least one thread-carrying implement, means for feeding work past said stitch-forming mechanism, complemental thread-severing members disposed at the same side of the work-support and movable relatively to each other into and out of thread-severing relationship, one of said members being confined to movement about a fixed axis and the other of sai-d members being bodily movable in a direction substantially parallel to its thread-severing edge, and means for simultaneously imparting the respective operative movements to said members during the thread-severing action of said members.

2. In a sewing machine having a work-support, in combination, stitch-forming mechanism including a needle and a complemental loop-taker, work-feeding mechanism, complemental threadsevering members disposed at the same side of the work-support and synchronously movable toward each other into thread-severing relationi ship, one of said members being supported for oscillatory movement and the other of said members being supported for rectilinear movement, and means for imparting the respective operative movements to said members during the threadsevering action of said members.

3. In a sewing machine, in combination, stitchforming mechanism including a needle and a complemental loop-taker, work-feeding means, a pair of movable thread-cutting members, and means for actuating said thread-cutting members including a movable connection carrying one of said thread-cutting members and operatively connected to the other of said threadcutting members, whereby the two members are caused to move into cooperation with each other during the severing of the thread.

4. In a sewing machine, in combination, stitchforming mechanism including a needle and a complemental loop-taker, work-feeding means, a first thread-cutting member, means supporting said first thread-cutting member for oscillatory movement, means for oscillating said rst threadcutting member including a connection operatively associated with said first thread-cutting member, and a second thread-cutting member carried on said connection and disposed to move into cooperative relation with said first thread-cutting member to sever thethread when said connection is actuated.

5. In a sewing machine, in combination, stitchforming mechanism including a needle and a complemental loop-taker, work-feedingv means, a' first thread-cutting member, a carrier supporting said first thread-cutting member and mounted for oscillatory movement, said carrier having a plurality of segmental teeth, means for oscillating said carrier including a connectionprovided with` a rack in mesh with said segmental teeth, and a second thread-cutting member actuated by said connection and disposed to be moved thereby into cooperative relation with said first thread-cutting member to sever the thread when said ccny nection is actuated.

6. In a sewing machine, in combination, stitchforming mechanism including a needle and a complemental loop-taker having a bobbinthread, work-feeding mechanism, a pair of bobt bin-thread-cutting members, means supporting one of said members for oscillation, means supporting the other of said members for reciprocation, actuating mechanism for imparting operative movements to said two members, whereby they move toward each other into thread-severing relationship, and means rendered effective by the movement of one of said thread-cutting members for urging the effective portions of said two thread-cutting members in shearing relation duri ing the thread-severing action.

'7. In a sewing machine, in combination, stitchforming mechanism including a needle and a complemental loop-taker, work-feeding mechanism, a first thread-cutting member, means sup-A porting said first thread-cutting member for oscillatory movement, means for oscillating said' connection is actuated, and a cam-element disposed in the path of travel of said second thread- Icutting member for flexing said second threadcutting member into shearing relation with said first thread-cutting member during the threadsevering action.

8. In a sewing machine, in combination, stitchforming mechanism including a needle and a complemental loop-taker having a bobbin, workfeeding mechanism, an oscillatory bobbin-thread pull-off and cutting device having a pull-off member and a rst knife member, a second movable knife member adapted to cooperate with said first knife member in severing the bobbin-thread, and means operatively associated with said bobbin-thread pull-off and cutting device and said second knife member for initially imparting oscillatory movement to said bobbin-thread pull-olf and cutting device to cause the pull-off member to engage and pull-off a measured length of bobbin-thread and to impart a further oscillatory movement to said bobbin-thread pull-off and cutting device and simultaneously to move said second knife member toward said first knife member to effect a severing of the bobbin-thread.

9. In a sewing machine, in combination, stitcha forming mechanism including a needle and a complemental loop-taker having a bobbin, workfeeding mechanism, a, bobbin-thread pull-offv member and a nrst knife member both disposed substantially in the same pla-ne, a movable com- -mon carrier for said members, a second movablel knife member adapted to be shifted into cooperative relation with said first knife member in severing the bobbin-thread, said second knife member being normally disposed at a level out of range of said bobbin-thread pull-off member, means for imparting operative movements to said carrier and said second knife member, and means to deflect said second knife member into threadshearing relation with said first knife member when said pull-off member has moved beyond said second knife member. 10. In a sewing machine, in combination, stitch-forming mechanism including a needle and a complemental loop-taker having a bobbin, a throat-plate, work-feeding mechanism, a bobbinthread pull-off member and a first knife member both disposed substantially in the same plane, a common carrier for said two members mounted beneath said throat-plate for oscillatory movement, a second knife member supported to move toward said first knife member for cooperation therewith in severing the thread, said second knife member being normally disposed at a level above the path of movement of said bobbinthread pull-off member, means for imparting operative movements to said carrier and said second knife member, and means to deflect said second knife member downwardly into threadshearing relation with said first knife member after said pull-off member has moved beyond said second knife member.

11. In a sewing machine, in combination, stitch-forming mechanism including a needle and a complemental loop-taker provided with a bobbin, a throat-plate having a clearance-channel, a carrier supported beneath said throatplate for oscillatory movement, a bobbin-thread pull-off member and a first knife member both secured to said carrier, means for actuating said carrier including a reciprocatory slide-bar operatively connected to said carrier, a second knife member mounted on said slide-bar and disposed to move toward said carrier into cooperative thread-severing relation with said first knife member, said second knife member having its effective portion disposed to travel in the clearance-channel of said throat-plate to avoid interference with said oscillatory pull-off member, and means for moving said second knife member into shearing relation with said first knife member after said pull-off member has moved beyond said second knife member.

12. In a sewing machine, in combination, stitch-forming mechanism including a needle and a complemental loop-taker provided with a bobbin, a throat-plate, a carrier supported beneath said throat-plate for oscillatory movement,'substantially coplanar bobbin-thread pulloff and first knife members secured to and extending substantially radially from said carrier, means for oscillating said carrier including an endwise reciprocatory slide-bar operatively connected to said carrier, a second knife member mounted on said slide-bar and arranged to move toward said carrier into cooperative threadsevering relation with said first knife member, said second knife member having its effective portion disposed at a level between said carrier and said throat-plate to avoid collision with said thread pull-off member during its active stroke, and a cam-element disposed in the path of travel of said second knife member to deflect the same into shearing relation with said first knife member during the thread-severing action of said knife members.

13. In a sewing machine, in combination, stitch-forming mechanism including a needle and a complemental loop-taker` provided with a bobbin, a throat-plate having a clearance recess formed in the bottom surface thereof, a disklike carrier oscillatably supported within said clearance recess with the bottom face of said carrier substantially flush with the bottom surface of said throat-plate, substantially coplanar bobbin-thread pull-off and first knife members secured to said carrier and operable within said clearance recess, means for oscillating said carrier including an endwise reciprocatory slidebar operatively connected to said carrier, a second knife member carried by said slide-bar and arranged to move toward said carrier into cooperative thread-severing relation with said first knife member, said second knife member having its effective blade-portion disposed at a level between said carrier and said throat-plate to avoid collision with said thread pull-off member during its active stroke, and a cam-element secured to said throat-plate and disposed in the path of travel of said second knife member to deflect the same downwardly into shearing relation with, said first knife member during the threadsevering action of said knife members.

14. In a sewing machine, in combination, with stitch-forming mechanism including a needle and a complemental loop-taker provided with a bobbin, and a throat-plate, of a bobbin-thread pull-off and trimming device, including an oscillatory disk-like carrier, a blade-like thread trimming knife iiatwise secured to said carrier, a blade-like thread pull-off member also atwise secured to said carrier in a position in advance of said knife in the direction of the active stroke of said carrier, said pull-off member and Said trimming knife having their effective edges disposed in substantially the same plane, and actuating means operatively connected to said carrier.

15. In a sewing machine, in combination, with stitch-forming mechanism including a needle and a complemental loop-taker provided with a bobbin, and a throat-plate, of a bobbin-thread pull-off and trimming device, including an oscillatory disk-like carrier having a plurality of gear teeth formed in its periphery, a blade-like thread trimming knife flatwise secured to said carrier, a blade-like thread pull-oft' member also filatwise secured to said carrier in a position leading said knife in the direction of the active stroke of said carrier, said pull-off member and said knife having their effective edges disposed in substantially the same plane, means for effecting a relative adjustment between said thread trimming knife and said pull-off member, and means for actuating said carrier including a rack in mesh with the gear teeth of said carrier.

ALFRED R. WOOD.

REFERENCES CITED The following referenloes are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,051,998 Horton Feb. 4, 1913 1,199,822 Rosenthal et al. Oct. 3, 1916 1,234,258 Barron July 24, 191'? 1,395,274 Hagelstein Nov. 1, 1921 1,820,569 Kiewicz Aug. 25, 1931 1,839,305 Fisher Jan. 5, 1932

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